Rhesus Monkey

The rhesus monkey, or rhesus macaque, is an Asian primate.MSN Encarta: Rhesus Monkey A rhesus monkey is red-faced with brown fur covering the body and head.Animal Diversity Web: Rhesus Monkey

The rhesus monkey reaches sexual maturity by three and a half to four years of age. Gestation period is between five and six months and females will reproduce every one to two years.The Humane Society of the United States: Rhesus Macaque (Monkey) A rhesus monkey will have one newborn at a time, weighing about 450 grams.BBC: Rhesus Monkey

The rhesus monkey is commonly used in scientific experiments. In 1940, Karl Landsteiner's research with rhesus monkeys led to the discovery of an antigen that causes rejection during blood transfusions. He named the antigen the Rh-factor, for the monkeys that enabled its discovery.BBC: Rhesus Monkey Genetics: Karl Landsteiner and the First Human Marker Locus (July 2000)